1. Field of Invention
The invention relates to a circuit board and a process for fabricating the same. More particularly, the invention relates to a circuit board having favorable reliability and a process for fabricating the same.
2. Description of Related Art
According to the current technologies, an embedded circuit board has been evolved from a common non-embedded circuit board. In particular, the common non-embedded circuit board is characterized in that circuits therein protrude from a surface of a dielectric layer. By contrast, circuits of the embedded circuit board are buried in the dielectric layer. Currently, a circuit structure of the circuit board is formed by performing a photolithography and etching process or a laser ablating process.
The fabricating process for forming build-up wiring structure of the embedded circuit board fabricated with the use of the laser ablating process comprises the following steps. A dielectric layer is formed on a circuit board having a circuit layer. Then, the surface of the dielectric layer is illuminated by a laser beam to form an intaglio pattern and a blind via connecting to the circuit layer. Thereafter, an electroplating process is performed to form a conductive layer filling up the blind via and the intaglio pattern. Herein, the build-up wiring structure of the embedded circuit board is roughly formed so far.
Since the depth of the blind via is different from the depth of the intaglio, the electroplating condition is not easy to be controlled when the electroplating process is performed, which leads to poor uniformity of the thickness of the conductive layer. Therefore, when a process for removing a portion of the conductive layer at the outside of the intaglio and the blind via is later performed, it is hard to control the thickness of the removed portion of the conductive layer. Hence, it is easy to improperly thinning the conductive layer of the embedded circuit board or leaving the conductive residue on the dielectric layer. Moreover, when the build-up wiring structure is fabricated on the aforementioned dielectric layer, the quality of the electroplating process is poor and the yield of the electroplating process is low. Therefore, the fabrication yield of the build-up wiring structure is decreased and the reliability of the circuit board is decreased as well.